Vehicle bumper systems are generally designed to serve two functions. The first function is to minimize visible permanent damage in the vehicle from low speed contacts with obtacles. Low speed collisions are generally defined as collisions at 5 miles per hour or less. The bumper system should withstand these low speed collisions without visible permanent damage, either to the vehicle bumper system or to the vehicle. Another function of a vehicle bumper system is to manage kinetic energy in a higher speed collision to avoid or reduce injury to the vehicle passengers. High speed collisions are those greater than 5 miles per hour. High speed collisions will likely result in visible permanent damage to either the vehicle bumper system or the vehicle. The way in which kinetic energy from the collision is managed through the bumper system and the vehicle is by providing a known and repeatable collapse of the energy absorbing subsystem.
It is desirable to manufacture a bumper that is both lightweight and have desired strength characteristics. Some current lightweight bumpers are manufactured with injection molded plastic material. Several U.S. patents have published designs for blow molded automotive bumper systems having an integral attaching bracket. The attaching bracket is generally made of metal and serves to attach the bumper system to the vehicle. Two brackets secure the bumper system to the vehicle. Each bracket is generally mounted near the outer edge of the bumper system and serve to transmit collision energy repeatably through the bumper system to the vehicle.
It is useful to provide a vehicle bumper system that has the required stiffness, yet is strong enough to minimize visible permanent damage in low speed collisions. Making bumpers sufficiently rigid to withstand both low speed collisions without visible permanent damage on the outside and higher speed collisions with proper kinetic energy management requires the use of thick blow molded wall sections and thereby increasing material cost and bumper systems' weight.
It has also been known to add foam within a vehicle bumper. Foam energy absorbers have been pre-molded and then assembled in place within the bumper. Use of such pre-molded foam blocks requires the use of adhesives or fasteners and large access holes to attach the foam to the bumper system. It is desirable to place foam within a bumper system without the need for adhesives, fasteners or large access holes.
Accordingly, it would be advantageous to provide a vehicle bumper system that is capable of withstanding low speed collisions without visible permanent damage, while providing an adequately rigid and strong cross-frontal area to controllably transmit kinetic energy from high speed collisions to the vehicle.
The primary object of the present invention is to provide a lightweight bumper for vehicles which avoids the shortcomings of the prior art.
Another objective of the present invention is to provide a bumper system for vehicles which is characterized by a relatively simple manufacture enabling relatively low assembly costs.
Yet another object of the present invention is to provide a bumper for vehicles which lends itself to mass production.
Still another object of the present invention is to provide a bumper for vehicles that is capable of withstanding low speed collisions without visible permanent damage, while fitting in limited packaging space allotted by the car designer.
These and other objects and advantages of the present invention will be more fully understood and appreciated with reference to the following description.